Chainring

ABSTRACT

A solitary chainring of a bicycle front crankset for engaging a bicycle drive chain, including a plurality of teeth formed about a periphery of the chainring. One or more clearance chamfer surfaces are formed on the chainring body, each of the chamfer surfaces substantially centered between adjacent pairs of the plurality of teeth.

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/311,735 and filed on Dec. 6, 2011.

BACKGROUND OF THE INVENTION

This invention relates to chainrings, and more particularly, to asolitary chainring for use with a conventional chain in a bicycledrivetrain system including a bicycle crank.

Bicycles and other chain-driven vehicles typically employ one or morechainrings and a set of rear hub mounted sprockets connected by a chain.Various mechanisms are used to maintain the chain on the chainring andsprockets. These mechanisms include chain guards, chain tensioners,chain catchers, derailleur configurations and so on.

While riding a vehicle with a chain-driven drivetrain, management of thechain and chainring engagement is particularly important to safe andeffective propulsion of the bicycle. Keeping the chain engaged with thechainring can be difficult, which is especially true of geared bicycleswhich can experience severe changes in chain tension and energeticmotion of the chain, especially when riding over rough terrain, as whileriding off-road, for example.

The invention provides an enhanced drive chain management, especiallyfor a bicycle that can successfully and reliably be ridden over roughand challenging terrain.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a solitary chainring of a bicyclefront crankset for engaging a drive chain. The solitary chainring,wherein solitary means only one, includes a plurality of teeth formedabout a periphery of the chainring, the plurality of teeth consisting ofan even number. The plurality of teeth includes a first group of teethand a second group of teeth arranged alternatingly between the firstgroup of teeth. The first group of teeth and the second group of teethare equal in number. Each of the first and second group of teethincludes an outboard side and an inboard side opposite the outboardside. Each tooth of the first group of teeth includes at least a firstprotrusion on the outboard side thereof and each tooth of the secondgroup of teeth is free of protrusions.

The invention also provides a solitary chainring of a bicycle frontcrankset for engaging a drive chain, the drive chain includinginterleaved inner and outer links, the chainring including a pluralityof teeth formed about a periphery of the chainring, the plurality ofteeth consisting of an even number. The plurality of teeth includes afirst group of teeth and a second group of teeth arranged alternatinglybetween the first group of teeth. The first group of teeth and thesecond group of teeth are equal in number. Each of the first and secondgroup of teeth includes an outboard side and an inboard side oppositethe outboard side. Each of the outboard side and the inboard side ofeach of the second group of teeth defines a recess formed in thechainring along each of the second group of teeth.

The invention also contemplates a bicycle crankset including a bicyclecrank arm and a solitary chainring attached to the bicycle crank arm andengageable with a drive chain. The solitary chainring includes aplurality of teeth formed about a periphery of the chainring, theplurality of teeth consisting of an even number, the plurality of teethincluding a first group of teeth and a second group of teeth arrangedalternatingly between the first group of teeth. The first group of teethand the second group of teeth are equal in number. Each of the first andsecond group of teeth includes an outboard side and an inboard sideopposite the outboard side. Each tooth of the first group of teethincludes at least a first protrusion on the outboard side thereof andeach tooth of the second group of teeth is free of the first protrusionson the outboard side and the inboard side.

These and other features and advantages of the present invention will bemore fully understood from the following description of one or moreembodiments of the invention, taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a top view of a conventional drive chain;

FIG. 2 is a side view of the conventional drive chain of FIG. 1;

FIG. 3 is a perspective view of a combined drive chain and chainringaccording to the invention engaged by a drivetrain;

FIG. 4 is a side view of the chainring according to the invention;

FIG. 5 is a close up of the chainring of FIG. 4;

FIG. 6 is a side view of a combined drive chain and chainring accordingto the invention engaged by a drive chain with the outer link platesremoved;

FIG. 7 is a front perspective view of the chainring according to theinvention;

FIG. 8 is a front perspective view of the chainring according to FIG. 7,engaged by a drive chain;

FIG. 9 is a rear perspective view of the chainring according to FIG. 7,engaged by a drive chain;

FIG. 10 is a front view of the chainring according to the invention;

FIG. 11 is a front view of the chainring according to the inventionengaged by a drive chain;

FIG. 12 is a cross-sectional view through line B-B of FIG. 5 of one typeof gear tooth according to one group of teeth;

FIGS. 13-15 are cross-sectional views through line A-A of FIG. 5 ofalternative types of gear teeth that are different than the tooth ofFIG. 12 and according to another group of teeth;

FIG. 16 is a partial side view of the chainring according to theinvention with rollers of a chain engaged with the teeth of thechainring;

FIG. 17 is a side perspective view of a chainring according to anotherembodiment of the invention;

FIG. 18 is a cross-sectional view of the chainring of FIG. 17 throughline D-D showing the profile of one of a second group of teeth;

FIG. 19 is a cross-sectional view of the chainring of FIG. 17 throughline E-E showing the profile of one of a first group of teeth;

FIG. 20 is a cross-sectional view of the chainring of FIG. 17 throughline F-F showing a clearance chamfer; and

FIG. 21 is a cross-sectional view of the chainring of FIG. 17 throughline F-F showing a clearance chamfer and with the structure adjacent thechamfer removed from the view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention will herein be described withreference to the drawings. It will be understood that the drawings anddescriptions set out herein are provided for illustration only and donot limit the invention as defined by the claims appended hereto and anyand all their equivalents. For example, the terms “first” and “second”or “left” and “right” are used for the sake of clarity and not as termsof limitation.

Referring to FIGS. 1 and 2 of the drawings, numeral 10 generallyindicates a conventional roller drive chain for a bicycle or any similarchain-driven device. The drive chain 10 generally includes outer chainlinks 12 and inner chain links 14 which are pivotally mounted on andconnected to the outer chain links by pins 16, 18. The outer chain links12 are alternatingly interleaved with the inner chain links 14.

The outer chain links 12 have paired outer link plates 20 and the innerchain links have paired inner link plates 22. Typically, rollers 24 arearranged around the pins 16, 18. The plates 20, 22 are provided withholes 30 at their ends 32. The pins 16, 18 typically extend through andproject out of the holes 30, although no projection at all is consideredto be optimal. The pins 16, 18 are externally riveted at their ends 34,36 during the assembly of the roller chain 10. While the pin 16 may bemade of round stock, pin 18 may be made of tube stock, as in the rollerchain 10 in FIG. 2. A narrow middle part 38, which helps to determinethe positioning of the roller chain 10, extends between the two circularends 32 of each of the outer link plates 20 and the inner link plates22.

As seen best in FIG. 1, and as viewed from above (or below) the chain,the interleaving of the outer links 12 and inner links 14 createscorresponding alternating outer link spaces 40 and inner links spaces42. Generally, the outer link spaces 40 are openings defined by theouter link plates 20 and rollers 24. Generally, the inner link spaces 42are openings defined by the inner link plates 22 and rollers 24.

The inner link spaces 42 are generally rectangular with the long axis ofthe rectangle aligned with the long axis (A) of the chain 10 (as viewedas in FIG. 1). The axial length of the inner link spaces 42 isdetermined by the distance between the rollers 24, while the distancebetween the inner link plates 22 determines the transverse spacing ofthe inner link spaces.

As seen in FIG. 1, the outer link spaces 40 are generally in the shapeof a “cross” or in other words, a “plus.” The axial length of the outerlink spaces 40 is determined by the distance between the rollers 24,while the distance between the outer link plates 20 determines thetransverse spacing of the outer link spaces.

It can be seen that the transverse spacing between the outer link plates20 is greater than the spacing between the inner link plates 22. Thus,because the transverse width of the rollers 24 determines the spacing ofthe inner link plates 22, the rollers dictate the transverse spacing D1of the inner link spaces 42. Similarly, since the outer link plates 20are positioned on the pins 16 (or 18) on the outboard sides of the innerlink plates 22, the transverse spacing D2 of the outer link spaces 40 isdictated by the sum of the transverse width of the rollers 24 and thethickness of two inner link plates.

Referring to FIG. 3, a chainring 50 according to the invention is usedwith a conventional chain 10. Chainrings typically have a largeplurality of teeth compared to cassettes, for example, having about 20or more teeth. A crank or crank arm 48 is in a typical position andattached to the chainring 50 in a well-known manner. The crank side ofthe chainring 50 is shown in FIG. 3, which is referred to as theoutboard side 54 of the chainring. The outboard side also faces awayfrom the frame to which it is attached, and accordingly may also bereferred to as the front of the chainring 50. The opposite of theoutboard side 54 of the chainring 50 is the inboard side 56. The inboardside 56 faces toward the vehicle.

Generally, force applied to the crank arm 48 (typically in a downwarddirection, for example) causes rotation of the chainring 50 in a likedirection (clockwise). Rotation of the chainring 50 causes the chain 10to be drawn over and advanced about the chainring.

The chainring 50 is in the general form of a ring-shaped chainring bodywith a plurality of teeth 52 formed about the periphery 51 of thechainring body, with the total number of the plurality of teethconsisting of an even number. The plurality of teeth 52 includes a firstgroup of teeth 58 and a second group of teeth 60 arranged in analternating fashion and wherein the first group of teeth is equal innumber to the second group of teeth. In a most general form, theinvention provides the first group of teeth 58 configured to be receivedby and fitted into the outer link spaces 40 and a second group of teeth60 configured to be received by and fitted into the inner link spaces42.

The overall shape of the chainring periphery 51 may be generallycircular or non-circular, that is elliptical, oval, polygon, orparabolic, for example. All of the examples of chainrings providedherein are circular at a periphery 51 thereof.

Each of the first group of teeth 58 is configured to engage with thechain 10 via an outer link space 40. Each of the second group of teeth60 is configured to engage with the chain 10 via an inner link space 42.

Turning to FIG. 12, each of the second group of teeth 60 has a shapewhich in a cross-sectional view is generally rectangular, particularlyat or near the base or root of the tooth. The cross-sectional view istaken through a plane parallel to the top land 80 of the tooth andpassing through the base circle position of the tooth, i.e., abouthalfway between the root circle and the outside circle.

The rectangular cross-section and overall width WO₁ of each of thesecond group of teeth 60 should closely match the configuration of eachof the inner link spaces 42 (FIG. 1). The cross-section shown of each ofthe second group of teeth shows that the outboard side 54 is generallyplanar and the inboard side 56 is also generally planar. Each of thesecond group of teeth 60 may fill over about 75% of the axial distanceD₁ of a corresponding space in the chain 10. Preferably, each of thesecond group of teeth 60 may fill over about 80% of D₁ of acorresponding space in the chain 10. More preferably, each of the secondgroup of teeth 60 may fill over about 85% of D₁ of a corresponding spacein the chain 10.

Turning to FIG. 13-15, each of the alternative versions of teeth 58 a,58 b, 58 c of the first group of teeth 58 (see FIG. 3) has a shape whichin a cross-sectional view, taken through the tooth as in FIG. 12, hasthe same longitudinal length L_(T) as that of the second group of teeth60 (FIG. 12). Each of the first group of teeth 58 may fill over about75% of the distance D₂ of a corresponding space in the chain 10.Preferably, each of the first group of teeth 58 may fill over about 80%of D₂ of a corresponding space in the chain 10. More preferably, each ofthe first group of teeth 58 may fill over about 85% of D₂ of acorresponding space in the chain 10.

Each of the first group of teeth 58 has the additional feature of anoutboard or first protrusion 62 on the outboard side 54 of eachalternative teeth 58 a, 58 b, and 58 c. FIG. 13 also demonstrates thatthe inboard side 56 of tooth 58 a can be the same (i.e., without aprotrusion) as the inboard side 56 of each of the second group of teeth60. The first protrusion 62 is configured to fit into the correspondingpart of outer link spaces 40 of chain 10 (FIG. 1) and has a width W₁.The protrusion 62 functions to help maintain the chain 10 on thechainring 50 (FIG. 3). The protrusion 62 causes an overall width WO₂ ofeach of teeth 58 a to be greater than the overall width WO₁ of each ofteeth 60 by the extent of protrusion 62.

FIG. 14 is another embodiment of a tooth 58 b of the first group ofteeth 58. In particular, tooth 58 b is similar to those of FIG. 13, withthe additional feature of an inboard or second protrusion 64 on theinboard side 56 of the tooth. The protrusion 64 has a width W₂ that isless than the width W₁ of the protrusion 62 of tooth 58 a, oralternatively, greater than W₁. The protrusions 62, 64 cause an overallwidth WO₃ of each of teeth 58 b to be greater than the overall widthWO_(E) of each of teeth 60 by the extent of protrusions 62, 64.Furthermore, WO₃ is greater than WO₂.

FIG. 15 is yet another embodiment of a tooth 58 c of the first group ofteeth 58. In particular, tooth 58 c is similar to that of FIG. 14, withan inboard or second protrusion 66 on the inboard side 56 of the tooth.The protrusion 66 has a width W₁ that is equal to the width W₁ of theprotrusion 62 of tooth 58 a. The protrusions 62, 66 cause an overallwidth WO₄ of each of teeth 58 c to be greater than the overall widthWO_(E) of each of teeth 60 by the extent of protrusions 62, 66.Furthermore, WO₄ is greater than WO₃.

It will be understood that the various configurations of the teeth 58include protrusions that are positioned along the side or sides of eachtooth in a position where they effectively function to assist inpositioning the chain on the chainring 50, including positions that areadjacent or at the base of each tooth or higher on each tooth 58.

FIG. 4 and FIG. 6 is an outboard side 54 of chainring 50 and the drivingdirection DD. The first group of teeth 58 is alternatingly arranged withthe second group of teeth 60.

The configuration of the second group of teeth 60 may be defined, withrespect to the outboard and inboard sides 54, 56 of each of the teeth60, by forming an inner link receiving recess 72 in the chainring 50that represents material removed from the sides of the teeth 60. Theinner link receiving recess 72 also serves to define the cross-sectionalshape of each of the group of teeth 58. The inner link receiving recess72 defines the outboard and inboard sides 54, 56 of each tooth andextends from the front flank 68 of one of the group of teeth 58 to arear flank 70 of an adjacent one of the group of teeth 58 in the drivedirection DD. Each inner link receiving recess 72 is configured toreceive the length L_(P) an inner link plate 22 of the chain (FIG. 6).Each recess 72 has a base surface 72 a that extends in an axialdirection and a wall 72 b (FIG. 7) that extends radially. The basesurface 72 a may describe a smoothly curving contour, and may begenerally in the shape of a “U”.

FIG. 5 is the profile of each tooth of the teeth 58, 60 in more detail.The inner link receiving recess 72 is formed in the chainring 50 and canbe seen extending along the side of each of the second group tooth 60and extending from the load side, front or leading flank 68 of one ofthe group of teeth 58 to a rear flank 70 of an adjacent one of the groupof teeth 58 in the drive direction DD. The recess 72 is configured toreceive the length L_(P) (FIG. 6) of an inner link plate 22. Each toothmay have a top land 80. The base surface 72 a may extend to the top land80 of each of the teeth 58. The front flank 68 of each tooth includes acontact zone 74, where a roller 24 (FIG. 1) contacts the tooth.

Above the contact zone 74 is an optional tip portion 76. The roller 24does not contact the tip portion 76 under normal driving conditions. Thetip portion 76 may protrude forwardly from a line drawn along thecontact zone 74 a distance T. The protruding tip portion 76 functions toengage a chain link earlier than a chain lacking the tip portion and toprovide better guiding of the chain.

An optional hook feature 78 is a feature that may be formed on the rearflank 70 of each of teeth 58, 60. The hook feature 78 is positionedalong the rear flank 70 and may cooperate with the tip portion 76 toprovide better guiding of the chain. The hook feature 78 may include aportion of the rear flank 70 aligned in the radial direction R.

Turning to FIG. 7 the first group of teeth 58 and the second group ofteeth 60 of the chainring 50 are arranged in an alternating fashion. Anoptional feature of each of the first group of teeth 58 and second groupof teeth 60 is a respective outer chamfer 82 a, 82 b. Each of the firstgroup of teeth 58 has an outer chamfer 82 a, which may be an arcuateface formed on the outboard side 54 or shoulder of each tooth. Each ofthe second group of teeth 60 has an outer chamfer 82 b, which may be anarcuate face formed on the outboard side 54 or shoulder of each tooth.The outer chamfer of 82 b of each tooth 60 may have an extent C₁ that isgreater relative to the extent C₂ of the outer chamfer 82 a of eachtooth 58.

Turning to FIGS. 8 and 9 the chainring 50 includes chain 10 positionedand engaged thereon. Outer chain links 12 are positioned on the firstgroup of teeth 58. Inner chain links 14 are positioned on the secondgroup of teeth 60.

FIGS. 10 and 11 respectively is a front view of the chainring 50 withouta chain 10 and with a chain. An optional feature of all of the teeth 58,60 of the chainring 50 is an offset OS of the center of the tooth tip ortop land 80 from the centerline CL in a direction toward the inboardside 56 of the chainring. This offset feature provides better guiding ofthe chain to one side of the chainring.

Turning to FIG. 16, a chainring 50 includes a number of teeth 58, 60.Link 1 of a chain engaged on the chainring 50 is represented by line L₁,and link 2 and link 3 are represented by lines L₂, L₃ respectively. Theline of each of L₁₋₃ is drawn between the centers of the axis of each ofthe chain rollers 24.

The hook feature 78 is shown on the rear flank 70 of each of teeth 58,60. The hook feature 78 is positioned along the rear flank 70 and maycooperate with the tip portion 76 of the front flank 68 to providebetter guiding of the chain. The hook feature 78 may include a portionof the rear flank 70 aligned in the radial direction R. The hook feature78 has a radially outermost extent 78 a where the hook feature and thelink centerlines L₁₋₃ intersect. Alternately, the outermost extent 78 amay be higher than the link centerlines L₁₋₃, providing more room forthe roller to engage the teeth in the driving direction. The curved line90 is the path of the roller 24 when it disengages the tooth.

In use, the chain 10 is installed with each of the outer chain links 12on one of the first group of teeth 58 and each of the inner chain links14 on one of the second group of teeth 60. As the chainring 50 isrotated by the crank 48, the chain 10 is drawn about the chainring, andthe outer chain links 12 and the inner chain links 14 are sequentiallyengaged with respective first and second ones of the groups of teeth 58,60. As detailed above, the various features of the chainring 50 functionto guide and maintain the chain 10 thereon.

FIGS. 17-21 show a bicycle chainring 150 that may share many of thefeatures of the chainrings described above. Generally, the chainring 150is a ring-shaped chainring body 150A with a plurality of teeth 150Barranged on the periphery thereof. The plurality of teeth 150B mayinclude alternating first and second groups of teeth 158, 160 and havingthe general shape and size of the teeth described above.

In one embodiment of the invention, an undercut 151 surface is formed atthe base of some or all of the inboard or second protrusions 166 formedon each of the second group of teeth 160 of the chainring 150.Alternatively, it will be understood that undercuts 151 could be formedon the outboard side of the chainring body 150A in a like position ofsome or all of the second group of teeth 160.

The undercut 151 may be formed by the removal or absence of material ofthe chainring body 150A at and below the base of each of the secondgroup of teeth 160. This has the effect of reducing the weight of thechainring 150. The absence of material leaves as much space as possiblefor mud, grass and so on to be ejected or moved out of the tooth gaps.Material of the chainring body 150A on the chainring side absent theundercut 151 may be left in place to provide stiffness to the chainring.

In this instance, the base of the second protrusions 166 forming thesurface of the undercut 151 means the radially most inward portion, faceor chamfer of each of the second group of teeth 160. The undercut 151 isshown best in FIG. 18, which shows, for comparison, the cross-section ofone of the first group of teeth 158, having no protrusions, positionedin front of one of the second group of teeth 160. Also, the undercut 151is shown in FIG. 19 in the cross-sectional view of one of the secondgroup of teeth 160.

Another chainring 150 according to an embodiment of the inventionincludes one or more clearance chamfers or clearance chamfer surfaces153 formed on the inboard side 156 of the chainring body 150A.Alternatively, the clearance chamfer surfaces 153 could be formed on theoutboard side 154 of the chainring body 150A opposite the inboard side156. In yet another embodiment, the clearance chamfer surfaces 153 couldbe formed on a combination of the inboard side 156 and the outboard side154 of the chainring body 150A.

Each of the one or more clearance chamfer surfaces 153 is substantiallycentered between adjacent teeth of the chainring 150. In one embodiment,a clearance chamfer 153 is substantially centered between every adjacentpair of teeth on chainring body 150A.

The clearance chamfer 153 is formed such that the chainring body 150Abecomes thinner as it approaches the radially outer periphery thereof.In other words, each clearance chamfer 153 is generally centered on oraligned with the bottom land 155 between adjacent teeth and is angledsuch that the chainring thins as the chamfer surface approaches thebottom land. The bottom land 155 may be of any thickness, includingforming a peak.

The clearance chamfer 153 is formed so as to not affect the shape of thetooth to any significant extent. In other words, the clearance chamfer153 is generally centered on the bottom land 155 between adjacent teeth,and extends to the tooth, the tooth root or the base of each tooth, butdoes not significantly alter the cross-sectional shape of the tooth.

The chamfer angle α of the chamfer 153 can be from about 5 degrees toabout 45 degrees from the radial direction R. In one embodiment, thechamfer angle α of the chamfer 153 is about 25 degrees from the radialdirection. FIG. 21 shows the radial direction R which, as illustrated inFIG. 21, also defines a radially-aligned center plane or centerline CLof the chainring body 150.

The clearance chamfer 153 contributes to the clearing of dirt, mud andother foreign materials from the chainring 150 and chain 10 (FIG. 1) toenable the proper seating of the chain onto the chainring. The undercut151 and the clearance chamfer 153 may both be used on the chainring 150.In the alternative, the chainring 150 may have one or the other ofundercuts 151 and clearance chamfers 153. While the clearance chamfer153 described herein may prove most useful in a chainring with at leastone group of teeth that substantially fills the space between the linksof a chain disposed thereon, it will be understood that the clearancechamfer surfaces 153 may be formed on a bicycle chainring absent thefirst and second groups of teeth.

While this invention has been described by reference to particularembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiments, but that it have the full scope permitted by thelanguage of the following claims.

1. A solitary chainring of a bicycle front crankset for engaging abicycle drive chain, comprising: a chainring body having aradially-oriented center plane, and an inboard side and an outboard sideon opposite sides of the center plane; a plurality of teeth formed abouta periphery of the chainring body; and one or more clearance chamfersurfaces formed about the periphery of the chainring body, each of theone or more clearance chamfer surfaces disposed between adjacent pairsof the plurality of teeth.
 2. The solitary chainring of claim 1, whereinthe one or more clearance chamfer surfaces extend from at least one ofthe inboard and outboard sides of the chainring body in a directiontoward the center plane of the chainring.
 3. The solitary chainring ofclaim 2, wherein the one or more clearance chamfer surfaces extend at anangle from about 5 degrees to about 45 degrees relative to the centerplane of the chainring.
 4. The solitary chainring of claim 2, whereinthe one or more clearance chamfer surfaces extend at an angle at about25 degrees relative to the center plane of the chainring.
 5. Thesolitary chainring of claim 2, wherein the one or more clearance chamfersurfaces are formed on the inboard side of the chainring body.
 6. Thesolitary chainring of claim 2, wherein the one or more clearance chamfersurfaces are formed on the outboard side of the chainring body.
 7. Thesolitary chainring of claim 2, wherein at least one of the one or moreclearance chamfer surfaces are formed on the inboard side and at leastone of the one or more clearance chamfer surfaces are formed on theoutboard side of the chainring body.
 8. The solitary chainring of claim1, wherein each of the one or more clearance chamfer surfaces extendcircumferentially from one of the adjacent pairs of the plurality ofteeth to the other of the adjacent pairs of the plurality of teeth. 9.The solitary chainring of claim 8, wherein each of the one or moreclearance chamfer surfaces extend circumferentially from a first base ofthe one of the adjacent pairs of the plurality of teeth to a second baseof the other of the adjacent pairs of the plurality of teeth.
 10. Thesolitary chainring of claim 1, wherein the plurality of teeth consistsof an even number; wherein the plurality of teeth includes a first groupof teeth and a second group of teeth arranged alternatingly between thefirst group of teeth; and wherein each tooth of the first group of teethincludes at least a first protrusion on the outboard side thereof andeach tooth of the second group of teeth are free of protrusions.
 11. Thesolitary chainring of claim 10, wherein each of the first group of teethincludes a second protrusion on the inboard side thereof.
 12. Thechainring of claim 11, wherein the first protrusion has a first widthand the second protrusion has a second width, wherein the first width isequal to the second width.
 13. The chainring of claim 11, wherein thefirst protrusion has a first width and the second protrusion has asecond width, wherein the first width is greater than the second width.14. The chainring of claim 11, wherein the first group of teeth eachhave a cross-shaped cross-section adjacent a base thereof.
 15. Thechainring of claim 10, wherein the second group of teeth each have arectangular-shaped cross-section adjacent a base thereof.
 16. Thesolitary chainring of claim 10, wherein the one or more clearancechamfer surfaces extend from at least one of the inboard and outboardsides of the chainring body in a direction toward the center plane ofthe chainring.
 17. The solitary chainring of claim 16, wherein the oneor more clearance chamfer surfaces extend at an angle from about 5degrees to about 45 degrees relative to the center plane of thechainring.
 18. The solitary chainring of claim 16, wherein the one ormore clearance chamfer surfaces extend at an angle at about 25 degreesrelative to the center plane of the chainring.
 19. The solitarychainring of claim 16, wherein the one or more clearance chamfersurfaces are formed on the inboard side of the chainring body.
 20. Thesolitary chainring of claim 16, wherein the one or more clearancechamfer surfaces are formed on the outboard side of the chainring body.21. The solitary chainring of claim 16, wherein at least one of the oneor more clearance chamfer surfaces are formed on the inboard side and atleast one of the one or more clearance chamfer surfaces are formed onthe outboard side of the chainring body.
 22. The solitary chainring ofclaim 10, wherein each of the one or more clearance chamfer surfacesextend circumferentially from one of the adjacent pairs of the pluralityof teeth to the other of the adjacent pairs of the plurality of teeth.23. The solitary chainring of claim 22, wherein each of the one or moreclearance chamfer surfaces extend circumferentially from a first base ofthe one of the adjacent pairs of the plurality of teeth to a second baseof the other of the adjacent pairs of the plurality of teeth.
 24. Thechainring of claim 11, wherein each of the second protrusions comprisingan undercut formed at the base thereof.